Desk operator&#39;s circuits



W. =A. RHODES DE$K 0 PERATORS CIRCUITS.

APPLICATION FILED DEC .5, 1918- Patented Sept. 26, 1922.

2 SHEETSSHEET I.

INVENTOR. W1 fifiadw J 2. 55%. ATTORNEY w; A. RHODES.

DESK .OPERATORS CIRCUITS.

APPLICATION FILED DEC.5,191 8- 1,429,9172.

2 SHEETSSHEET 2 )6 N Xg/QQ 3Q INVENTOR. 140i fi/wder BY Z 5 L.

. ATTORNEY m wv Patented Sept. 26, 1922.

certain Improvements in 'cuits,

Patented S tugfi, 1922 1,9,

S T ATENT" FF R- WILLIAM A. RHODES, or NEW YoRK, N. Y., Assienoaro AMERICAN TELEPHONEAND TELEGRAPH COMPANY, ACORPORATION or NEW YORK.

DESK oPEn'ATons CIRCUITS. Application filed'December 5, 918. Serial 110,265,435.

the trunk key, which result in autoinati cally disconnecting the operators' set from the monitoring cord and connecting itvvith the trunk without withdrawing the plugfrom the monitoring jack. i i I of the invention relates T 0 all whom it may concern.

Be it known that I, WIL IAM A. RHODES, residing at New York, in the county of New York and State of New York, have invented" Desk Operators Circuit's, of which the following is a specification.

This invention relates to telephone cirand more particularly to circuits whereby connections maybe established to special operators" positions.

in accordance with this invention a desk circuit is provided for a special operator, such has'a chief operator, and equippedywith a single ended cord for eithertalking or monitoring, and with terminal equipment for monitoring lines, tie lines, trunks 'from the switchboard at the A operators positions, and lines to supervisors. The circuit is arranged for reducing inductive discharges and receiver disturbances particularly when machine ringingis tripped upon answering a call over a trunk from the switchboard, and for monitoring upon an operatmrs or supervisors line through a high impedance monitoring circuit. The circuit also arranged for ringing out on a tie line, or trunk, or for ringing over the monitoring cord by means of a common ringing key, a talking key being also associated with the cord whereby the operator may talk over the monitoring cord. The arrangement of the circuit is such that the desk operator may perform routinemonitoring work and may answer an incoming call or make an occasional outgoing call without being required to disconnect the monitoring cord or to operate a key for disconnecting this cord from her set, such disconnection being automatic upon the operation of any key by which the operators set is connected to some other circuit;

One of the features of the invention con in the provision of means whereby the desk opcrators receiver is normally connected to a monitoring cord, preferably through a high impedance coil, so that the operator may monitor any connection by simply inserting the plug of the monitoring cord in the jack associated with the desired connection.

Another feature of the invention relates to the arrangement of the circuit, so that no other operation is necessary for answering a call incoming from a trunk than throwing A further feature tothe provision ofmeans whereby the desk operator, in answering a trunk call by throwing the trunk key, trips machine ring-c ing andautoniatically connects the desk op? eratorssetto the trunk, after a substantially uniform interval'suificient to allow the electrical conditions of the circuit to reach a state of equilibri nn, theinterval'being the same regardless of variationsin the potential of the battery supplying current to op} crate the relays whereby the connection is made. This result is accomplished by pro vidi'ng two relays, one being s'lowlto attract its arn'iature and the other being slow-releasing, said' relays jointlycontrolling the connection of the operato rs set. I i

A further'featureof the invention ,consists in the provision of afi'holding key, whereby a call incomingover atrunk may be hcld, and the operators set maintained disconnected from I the monitoring cord, ready'to be connected to another trunkfafter the usual interval following the operation of thetrunk key. i

A still further feature of the invention're sides in the arrangement of means whereby the operators set may be immediately connected'for talking over the monitoring cord or over a tie line extending toanother desk, by manipulation of a talking key.

Still another feature resides inthe provision of means whereby ringing current may I be applied to any one of several trunks or c to the monitoring cord by the operation of a common ringing key, instrumentalities being provided wherebyflthe operation, of a' trunk key ariton'iatically prevents ringing current from being applied to those contacts of the common ringing sa which are associated with the monitoring cord. i An additional feature ofthe invention has reference to the operators set which is so arranged that calls may, if desired, be answered .by an ordinary desk telephone set, but when the operator is usinga head receiver the call may be answered by using" said receiver and the transmitter of the desk stand, without removing the receiver of the desk stand from the hook. When the op-' erator is using a chest transmitter and head receiver, the apparatus is arranged so that incoming calls may be answered by means of these instruments without removing the desk stand receiver from the switch hook, the transmitter of the desk stand being at the same time rendered inoperative.

The invention may now be more fully understood from the following description when read in connection with the accompanying drawings, Figures 1 and 2 of which when placed end to end constitute a circuit diagram of a preferred embodiment of the invention.

Referring to the drawing, a desk circuit E is shown provided with a desk stand telephone set S and auxiliary telephone sets S and 8,, the set S consisting of a head receiver 1 and chest transmitter 2 and the set S consisting of a head receiver 3: The circuit E is provided with twin jacks J and J whereby sets S and S may be associated with the circuit E through twin plugs P and P The circuit E is also provided with a controlling key K whose contacts are so arranged that the receiver of one of the three operators sets is normally connected through a high impedance transformer 4 and over conductors 5 to the contacts of a monitoring plug P The operators circuit E is further provided with conductors 6 and 7 to which the operators set may be connected, these conductors being provided with a plurality of branches which lead to the connections of a plurality of trunks such as T T etc.

The trunk T shown in the drawing is illustrative of a group of trunks leading to A operators positions, where they terminate in jacks such as the ack J. A trunk key such as K, is provided .ior each trunk of this type, said key being arranged so that when thrown to the left the conductors 6 and 7 are connected to the trunk, and the operators set connected to the corn ductors 6 and 7 by means of a relay 8 after a suitable interval determined by the operaation of a slow-operating relay 9 and a slow releasing relay 10. This combination of relays is provided in order that a sulficient interval will elapse after the opera tion of the key to permit of tripping the ringing current applied to the trunk before the operators set is connected thereto. The relay 8 is so arranged that in connecting the operators set to the trunk over conductors G and 7, the set is automatically disconnected from the plug P so that the plug need not be withdrawn from the jack of any circuit over which the operator may have been monitoring. In order to illustrate the operation of tripping machine ringing, a subscribers set A is shown connected over a line L, and an A operators cord C terminating in a plug P, to the trunk T the connection being completed by inserting the plug P of the A operators cord circuit in the jack J of the trunk. The equipment of the cord circuit is of a standard type well known in the art and need not be further described.

The trunk T is illustrative of a type of trunk which extends between two operators desks and is commonly known in the art as a tie line. This trunk terminates at each end in trunk keys such as K and K whereby the operators circuit E with its associated set and a similar or equivalent set B may be connected to the trunk. The trunk T in addition to the talking conductors, is provided with a third. conductor over which signals may be t ansmitted from one desk to the other by simply throwing the key K or K as the case may be. As ringing is not employed for signaling over a trunk of this character, the ,key K is so arranged that the operators set is connected to the trunk imn'iediately, without the interposition of the time interval employed inconnection with trunks of the type of the trunk T At-T,, is shown a trunk which illustrates the manner .in which the monitoring cord tern'iinating in the plug P may be employed. The trunk T terminates in a jack J, and connects to the line L which is in connnunication with an operator provided with the operators set D. By inserting the plug P in the jack J the operator at E is enabled to monitor on the line l by means of the trunk T, and check the work of the operator at D.

In order that the key K may be used for ringing either over the monitoring cord 5 or over trunk connections of the type T a relay 16 is provided which controls the application of ringing current to certain of the left hand contacts ot the key K, whereby ringing current may be applied to the plug P The relay l6 is included in series with the relay 8 which connects the operatofis set to trunk cmmections and is operated whenever a trunk key such as K is actuated. In order to ring over a trunk such as T the trunk .key K .must be thrown to the left, thereby causing the energization of relay 16, which disconnects ringing current from the contacts whereby ringing current may be applied to the plug 1? lonsequently, when the key K thrown to the left, ringing current is applied over the outer contacts of said. key to the trunk corresponding to the actuated trunk key, but ringing current is not applied to the monitOriIlg' cord. If no trunk key is operated to connect the set at E to the trunk, the actuation of the key K to the left will apply ringing current over the monitoring cord 5 to the plug P since the relay 16 will not be energized, and ringing current will conductors 14 and 15, IlOllllLllQflJ' hand The details of the a aratusanyh w' be best understoodffrom the operation, which is, as ing that the chief operat monitor on the connectionlat L any onset the telephone sets S S or B5 maybe eniployed, Ifthe setid is employed the plug P will be inserted in t'le jack J and the receiver 3 will be connected over the ring contacts of the plug and jack, over conductors 11, inner back contacts ef relay 8,

a description of impedance transformer 41;; over 13 normal. right hand contacts y t 9 tacts of key K and conductors 5 to the tip and ring contacts of the 'plug P By simply insertingthe plug P in the jack J therefore, the chief operators receiver 3' is connected over the trunk connection at L 'may be observed.

Should the operator at E I w the operator at D, the key K may be thrown to the right, thereby completing a circuit from battery over the upper right hand make contact of key K, ever the sleeve contacts of the plug P and the jack J and through the winding of the relay 1'? to ground; Relay 17 upoinbeing energized causes the lamp 18 'toglow; thereby informing the operatorat D that a call awaitsher. Over the lower right hand make contact oil the key K, a circuit is closed from ground through the winding of relay 16, and through the winding of relay 8 to battery. Relays 8 and 16 are energized over the cirs cuit above traced, the latter disconnecting ringing current from certain of the left hand contacts of key 1C and the former op erating to disconnect the receiver circuit 11 from the high impedance transformer-l and connectsaid receiver circuit in shunt with one of the secondary windings of the tranr former 19.

The plug P is connected to the talking apparatus associated, with the transformer 19 over the contacts of the key K as follows plug P conductors 5, inner left l nor mal contacts of key K, conductors 1 1; and 15 inner right hand make contacts of key K, conductors 20 and 21 and conductors 6 and 7, to transformer 19. The operator at E is now enabled to talk over the monitoring cord without removing the receiver 2-2 of the set S from the hook. This arises from the facts th at the insertion of the plug P in the ack,

J closes a pair of contactsQB which are con nected in parallel with the switch hook contacts, so that an energizing circuit for the transmitter 24- is completed from, battery through the impedance coil 25, over the back contact of relay 26, over contacts 23 oiF-the jack J through the trimsmitter 24- aud priground.

follows Assumor at E wishes" to T so that the desire signal 1 tery through the impedance mary windings of the transformer 19 to ,Incase the operatoratE had been using the set 5 including the chest transmitter and the headreceiver 1, the transmitter 24 egt S ldpot be employed in talk- 1 111g over the circuit above described, but the I transmitter and receiver or the set S would beused. In thiscase the plug ,P would have been inserted in the-jack J closing contacts :2? in parallel with the switch hook contacts. The closing of contacts27 is,1howv "ever, without any useful eiiect, as the cirback' contacts of relay '12; through high v i conductors c of key Ky:

ftion ofa relay 26cver a circuit as followsr' cuitj forithe transmitter 24: which would otherwise have been completed over these contacts is at onceopened by the energiza from battery, throughthe winding of relay 26, over the lower tip contacts of jack J and plug P through the transmitter 2311pper tip contacts of plug through the 1 primary former 19,to ground. Relay 26 upon attracting its'armature opens the circuit of the transmitter 24 and completes the battery supply circuit, for transmitter 2 from batfront contact of relay 26,;and thence over the circuit previously traced through transmitter 2 to ground. The receiver 1 is, of course bridged across the conductors 11, so thatit is connected in shunt with the lower secondary windingof the transformer 19. The transmitterQ andthe receiver 1 may therefore, be employed-in talking over the monitor-in circuits, without regard to the desk stand set'S If the operator at E had been employing neither the head receiver 3 of the set S 'nor the chest transmitter and head receiver of the set S}; the desk stand set S would have been used by removing the receiver at 22 from the switch hookinltheordinary manner and talking into the transmitter 24. The removal of receiverQQfrom the switch hook connects said receiver across conductors 11 I over the switch hook contacts, and a circuit for the transmitter Qiis completed over the switch hook "contacts from battery through theimpedance coil 25, back contact of relay 26,,switch hook, contacts of the set S of. inductance coil 19 to ground. If the operator at E desires to'ring over the monitoring cord terminating in the plug P the key K may be, thrown to the left.

The circuit otrelays ,8 and 16 will now be open, and these relays will be deenergized so that ringing ciilrrent is connected over the shack contacts of relay 16, over conductors 28, inner left hand make stored to normal and the plug P inserted P and jack J and windings of trans- 25 over the v through the transmitter 24 and primary I windings in the jack J3, the operator at E is monitor ing over the trunk T using the head receiver 3, and that a subscriber at A, whose line L terminated before an A op'erators position, has been connected by an A operators cord circuit C to the trunk T, byinserting the plug P in the jack J of said trunk, a circuit is completed from ground over the sleeve contacts of jack J and plug P, through the winding of the sleeve relay 29 and lamp 250 to battery. Relay, 29 completes a circuit from ground over its front contact, over the back contact of tripping relay 31, back contact of relay 32, and

"through the winding of relay to battery.

Relay 33 is energized and applies ringing current through the winding of tripping relay 31 and over its front contacts 'to the trunk T thereby energizing the ringing responsive relay {Set of the trunk. Relay 3st upon being energized completes a circuit from battery, over its front contact and through resistance and the winding of relay 36 to'ground. Relay 36 at its front r contact completes a circuit for the lamp 8? and establishes a locking circuit for its own winding from battery, over its front contact and through the resistance 35 and, the winding of relay 36 to ground. v

T he operator at E upon observing the glowing of the lamp 37 operates the trunk key K, by throwing it to the left and thereby short circuiting the winding of relay 36 and el'l'acing the lamp 237, and bridging the winding of relay 88 across the trunk T The es tablisln'nent of this low resistance bridge in shunt with the high impedance bridge through relay 34:, reduces the resistance of the trunk circuit to such an extent that the tripping relay 31 is energized, thereby opening the short circuit about the winding of relay 32 which is accordingly energized and short circuits the winding of the ringing re" lay 33. The ringing relay 33 is (leenergized and disconnects ringing current from the trunk, the relay 32 being at the same time locked up over its lower front contact. lhe direct current path through the winding of relay 38 also results in the energization of the supervisory relay 39 of the cord circuit C, so that the lamp 30 is shunted, and no longer continues to glow.

The relay 38, upon being bridged across the trunk T, is energized by current flowing through its windings, and operates in a manner about to be described, to connect the operators set at E to the trunk, after an in terval sufiiciently long to permit of the tripping of the ringing current and other oper ations just described, so that the operator at E does not receive any click due to these operations. The relay 38 at its front contact completes a circuit from ground over the lower back contact of relay 8, and through "the winding of the slow-acting relay 9 to through the winding of relay 16 and through the winding of relay 8 to battery. Relays 8 and lo areenergized, the latter disconnecting ringing current from the contacts of the key K and the former operating as already described to bridge the receiver 3 across the winding of the transformer 19. The transmitter 2 t of the desk stand set may be used .by the operator at E in answering the call 'wlthout removing the rccelver 22 from the switch hook, since the circuit of the transmit ter is'coinpleted in the manner already described, and said transmitter is connected through the transformer 'l i) over conductors (l and 'Z and the outer left hand normal contacts of key is: to junction points 4H) and ll,

the connection extending from said junction points over the left hand make contacts of trunk key l e, to the trunk T It will be noted that the operators setis connected interval of time to the trunk 1, an alter the operation of relay 38 determined by the amount of time necessary for.

"the slowed-ting relay 9 to pull up its arn1a turc, and for the slow-releasing relay 1() to perm it its armature to retract, the two operations taking place in succession. The

amount of time necessary for these two operations will always be substantially the same for Variations in battery potential met with in flhmfilte. If the potential of the battery is high, the relay fl will atract its urmatlu'e more quickly, but this shortening of the time interval is ccm'ipensated for by the fact that the slmwrelcasing relay ll) correspondingly slower in releasing its armature, so

that the total time for the two operations will be substantially the same. Similarly, if the potential of th'ebattery is low, the increased amount of time taken by the relay 9 in attracting its armature compensated'by the shorter interval required for the relay ll) to release. This is an important v feature of theinvention, as it provides a me necting the operator. set to the trunk a pre determined and uniform interval of time after the operation of the trunk key.

Should the operator at E desire for any reason to hold the call incoming on the trunk T the key K, may be thrown to the right, thereby bridging a coil'l-2 across the trunk T, and completing a circuit over the lower right hand make contact of said key K, and

the winding of relay upper front contact of relay 8', and front conthrough the winding ot :reiay 12 to battery. The relay 12 upon being. energized holds openthe connection :t'rom the receiver circuit tact of relay 38 to ground. At its lower contact relay 8 opens a circuit originally traced for relays 9 and 10, so that both of these relays are restored to normal. Consequently,

as soon as the key K, is thrown to its right hand or holding position, relay 88 isdeenergized due to the fact thatit isno longer bridged across the trunk and, uponreleasing its armature, said. relay at once opens the locking circuit of relays 8 and 16 which are restored to normal, the receiver, however, being maintained disconnected from the monitoring cord 5 byxineans of the relayl2. lVith the circuitin this condition the operators set may be connected to-any other trunk by operating the trunk key;.corre+ sponding to that trunk the usual time interval being introduced by the operation of relays 9 and 10 as before describec. If an operator at B should desire to comnnniicate with the operator at E over the tie line trunk T said operator at l3,will actuate the key K thereby connecting her talking set to the trunk T and completing a circuit over the lower contact of said key through a resistance 43 and through the winding of signal controlling relay 44 to battery. Relay 44 upon being energized attracts its armature and completes a circuit from battery, through the winding ofrelay 44, over the front contact of said re lay, over the third conductor of the trunk T over the back contact of a relay 45 at station E corresponding to thefrelay 244 at station B, and through the. winding of a' signal responsive relay 46. ,The circuit just traced locks up the relay 44 independent of the key K and results in the cnergizatiou' of the relay 47 to glow, calling the attention of the operator atl l to the fact that a call is waiting upon the tie line To. i

The operator at E, who may; at this time, have been monitoring over the cord 5, now;

throws the key K Without withdrawing. the

' plugP from the monitoring jack; The

operation of key- K causes the energization of relay 45 over a restored to normal.

46 which causes the signal lamp;

I lower make contact of. said key. Belay 45, upon attracting its armature, opens the circuit of relay 46, thereby effacinglamp 47 and establishing a locking circuit for the relay 45 from battery, through thewindingand overthe front contact of relay 45, over the third conductor of the trunk T and over the front contact of relay 44, through'resistanoe- 48, and over the lower make contact-of key K, to ground.

At the same timea new locking circuit is completed for-the, 'relay'44. from battery, through the winding and over the front contact of said relay, over the third conductor of; the trunk, over the. front contact of re' lay45 ,and over the loWermakecont-act of KeyK to ground. It willbe seen that both relays 44andy45 are maintained energized ,over circuits jointly controlled by the keys K and K so that ifeither operator should restore her key, both of these relays willbc maintained energized-to prevent a false operation of the signal lamp which. would Otherwise occur; As soon as both operators have-restored their keys, however, these relays will deenergized and the circuits Itwill be noted that the arrangement of signal; controlling and signal responsive relays, as well as the signallanips and keys atthe two ends of the trunk, are identical, so thatcalls may be Inadein either directonin the same manner as that already described.

When theiopera'tor at E actuates the key K in response to the; signal lamp 47, in addition to the operations already described, the actuation of said key closesa circuit. from ground, over the lower make contact of said key, through the windingof relay, 16, and through the winding of relay 8 to battery. Relays 8 and 16 are energized, latter "disconnecting ringing current from certain contacts of the keyii and the former, operating to disconnect the monitoring receiver- 3 from. themonitoring cord 5, and

to connect theoperators set overthe conduo I sary in this case, as ringing current is not em loyed in connection'with the tie line T hould the operator at E desire to ring over a tie line trunk Snob at T which is arranged for ring-down operation,@the key K of such trunk will be actuated, thereby coin pleting the circuit already described for rethe slow-acting relays 9 and 10. This lIltGIVLllS not access lays 8 and 1 6. The. operator then throws the key K to the left, so that ringing .cur-

rent is applied, over the outer left hand make contacts of said key and over the make contacts of the trunk key such as K,, to the trunk. The energization of relay it) prevents ringing current from being applied over the contacts of said relay and over the inner left hand make contacts of the key K to the monitoring cord 5. It will be seen, therefore, that the arrangement of the key K and relay 16is such that the key K may be used for ringing either over a trunk, or over the monitoring cord independently, the ringing current being applied only to the trunk it a trunk key is actuated, since the energizationof relay 16 prevents ringing enrrent'lrom being applied to the monitoring cord,- and ringing current being applied only to the monitoring cord if no trunk key is actuated, since in this case the relay 16 will be maintained deenergized and no path for ringing current over the trunk will be provided by the trunk key. y

By means of the circuit arrangement above described the desk operator may perform routine monitoring work and answer incoming calls, or make occasional outgo ing calls, without disconnecting the monitoring cord or operating a special key for disconnecting this cord -from her set, such disconnection being automatic upon the operation of any other key. Furthermore, it will be obvious that the general principles herein disclosed may be embodied in many other organizations widely difierent from that illustrated, without departing from the spirit of the invention as defined in the following claims.

hat is claimed is:

1. In a telephone system, a monitoring cord, an operators set, switching means normally connecting the operators set to the monitoring cord, a trunk connection, switch ing means for the trunk connection, and means whereby when the switching means of the trunk is operated the operators set is disconnected "from the monitoring cord and connected to the trunk by said first mentioned switching means.

2. In a telephone system, a monitoring cord, an operators set normally connected thereto, a plurality of trunk connections, switching means for the trunk connections, and means whereby when the switching means of a trunk is operated the operators set is disconnected from the monitoring cord and connected to the trunk, after a predetermined interval. r

3. In a telephone system, a monitoring cord, an operators set normally connected thereto over a high impedance path, a plurality of trunk connections, switching means for the trunk connections and means whereby when the switching means of a trunk is operated the operators set is disconnected from-the monitoring cord and connected to the trunk over a low impedance path.

4:. In a telephone system, a monitoring cord, an opcratofs set normally connected thereto over a high impedance path, a. plurality of trunk connections, switching means for the trunk connections, and means whereby when the switching means of a trunk is operated the operatofs set is disconnected from the monitoring cord and connected to the trunk over a low in'ipedance path, after a predetermined interval.

5; In a telephone system, a. monitoring cord, an operators set normally connected thereto over a high impedance path, a plurality of trunk connections, switching means {or the trunk connections, and means whereby when the switching means of a trunk is operated the operators set is disconnected from the monitoring cord and connected to the trunk over a low impedance path, after a predetermined interval and whereby when the switching means is restored the operators set is immediately disconnected from thetrunk.

6. In a telephone system, a monitoring cord, an operators set normally connected thereto, a trunk circuit, a trunk key and a holding key therefor, means whereby when the trunk key is ope 'ated the operators se will be disconnected from the monitoring cord and'connected to the trunk, and means whereby when the holding key is operated. the operators set will be maintained disconnected from the monitoring cord and from the trunk. ,e

7. In a telephone system, a monitoring cord, an operators set normally connected thereto, a plurality of trunk circuits, trunk keys and holdin keys therefor, means whereby when any trunk key is operated the operators set will be disconnected from the monitoring cord and connected to the corresponding trunk after a predetermined interval, and means whereby when the holding key of a trunk is operated the operators set will be maintained disconnected from the corresponding trunk and the monitoring cord and in condition to be connected to any other trunk a predetermined interval after the operation oi the trunk key thereof.

8. In a telephone system, a monitoring cord, an operators set normally connected thereto, a plurality of trunk circuits, trunk keys and holding keys therefor, means whereby when any trunk key is operated the operators set will be disconnected from the monitoring cord and connected to the corresponding trunk, and means whereby when the holding key of a trunk is operated the operators set will be maintained disconnected from the corresponding trunk and the monitoring cord and in condition to be connected to any other trunk upon the operation of the trunk key thereof.

9. In a telephone system, a trunk, an operators telephone set,a circuit over which said set may be connected to said trunk,

switching means for said circuit, and means responsive to the actuation of said sn-iitching means to connect said set to said trunk over said circuit after a predetermined interval, said means including a slow attracting relay and a slow releasing relay.

10. In a telephone system, a trunk, an op erators telephone set, a circuit over which said set may be connected to the trunk, switching means for associating said circuit with the trunk. a slow attracting relay and a slow releasing relay, and means responding to the actuation of said switching means, after said slow attracting relay has operated and said slow releasing relay has in turn released, to connect said set to said circuit. v

ll. In a telephone system, a trunk, an operators set, a transmission circuit over which said set may be connected. to the trunk, switching means for associating said circuit with the trunk, a slow attracting relay and a slow releasing relay, meansoperating upon the actuation of said switching means to complete circuits for said relays, means to open the circuit of the slow releasing relay upon the energization of said slow attracting relay, and means responsive to the energization of said slow attracting relay a'tter the release of said slow releasing relay to connect said set with said transmission circuit.

12. In a telephone system, a, line circuit, a trunk leading to a special position, a link circuit for connecting said. line circuit to said trunk and applying ringing current to said trunk, an operators set at said special position and switching means there for, means responsive to the actuation of said switching means to disconnect the ring-- ing current trom the trunk, and means responsive to the actuation of said switching means to connect said operators set to said trunk after a predetermined interval, said last mentioned means including a slow attracting relay and a slow releasing relay.

13. In a telephone system, a. line circuit, a trunk leading to a special position, a link circuit for connecting saidline circuit to said trunk and applying ringing current to said trunk, an operators set at said special position and switching means therefor, means responsive to the actuation of said switching means to disconnect the ringing current from the trunk, a slow attracting relay and a slow releasing relay, and means responsive to the actuation of said switching means to connect said operator s' set with the trunk after said slow attracting relay has operated and said slow releasing relay has thereafter released.

14. I11 a telephone system, a plurality of trunks, an operators telephone set, switching means for each trunk, means responsive to the actuation of the switching means of a trunk to connect said set to the trunk after a predetermined interval, said means includin a slow attracting relay and'a slow releasing relay, means whereby when the switching means is restored said set is i111 mediately disconnected, said relays then being in condition to connect the set to an other trunk, a predetermined interval after the actuation of the switching means of said other trunk.

15. In a telephone system, a ring-down trunk, a direct current signaling trunk, an operator's set, switching means whereby said operators set may be connected to said ring-down trunk, a predetermined interval after the switching means has been actuated, and switching means operating to immediately connect the operators set to the direct current signaling trunk. is

16. In a telephone system, amonitoring cord, a trunk connecting circuit, an operators set adapted to'be connected either to said cord or said circuit and a common ringing key for applying ringing current either to said trunk connection or said cord exclusively.

17. In a telephone system, a monitoring cord, an operators set normally connected I thereto. a trunk, a transmission circuit over which said set may be associated with said trunk, switching means for disconnecting said set from said cord and connecting it to said trunk over said transmission circuit, a common ringing key having contacts for applying ringing current to said trunk and other contacts for applying ringing current to said cord, and means responsive to the actuation of said switching means to disconnect ringing current from said last mentionedcontacts, whereby when said switch ing means are actuated together with said ringing, key ringing current is applied to said trunk only and whereby when said ringing key is actuated ,alone ringing current is applied to saidcord only.

In. testimony whereof I have signed m name to this specification this third day. of December, 1918.

WILLIAM A. RHODES. 

